| 摘要 |
PURPOSE:To enable the level of either trip point to vary with the contrast of an original, by providing the operation of a comparator with two trip points with hysteresis characteristics. CONSTITUTION:Analog comparator 2 switches analog signal (a) from input terminal 1 at two trip points to convert it into digital signal (g). Then, amplifying circuit 4 amplifies analog signal (a) to a level needed for integrating circuit 5 to operate. The integrating circuit performs by analog signal (a) integration with an adequate time constant to obtain signal (d) corresponding to the contrast of an original. Level change-over circuit 6 changes the level of signal (d) over to signal (e) further adequate to the contrast of the orginal. Receiving signal (g) as an input, inverter 7 controls the ''-'' terminal of comparator 2 by inverted signal (b) through diode 8 to generate the timing of one fixed trip point between two trip points. Diode 8 controls signal (e) by signal (b) to generate the level of the fixed trip point. |
